Silicone Brake Fluid in a 58 Caddy HELP!!!!!!

[FireballV8]

Hi

I just replaced all the brake components on my 58 Cadillac Series 62. I would like to use DOT 5 brake fluid with silicone and want to know what your experiences have been?

Should I use it or should I stick with regular brake fluid?

Thanks

[The Old Guy]

If the car has a hydraulic stop light switch, carry a spare as it has been my experience that silicone fluid will make them inoperable after awhile. Some last indefinitely, and some only make it a year.

[mrpushbutton]

I am a big believer in silicone brake fluid. I worked for 12 years as a mechanic for a large vintage car collection (over 100 cars) and we had one of everything in terms of engines, transmissions, brakes, electrical systems--we saw it all. The cars that were set up with silicone brake fluid ALWAYS had good brakes, even after sitting in storage for years. The Dot-3 (regular brake fluid) cars were hit and miss. Some were OK, others had no brakes, the fluid had turned to Jello inside the master cylinder or the alloy pistons had welded themselves into the wheel cylinder bores by electrolysis.

A couple of things if you are going to go over to silicone:

You need to take apart the (hopefully NEW) wheel cylinders, wash the metal parts with lacquer thinner, the rubber parts with denatured alcohol--this gets the shipping cosmoline off of the parts. You then need to coat the parts with whatever fluid you are going to run the system on--is silicone, coat with silicone. If Dot-3, coat with dot-3.

If you have not replaced the hard lines, you need to flush them out, there is residual dot-3/paint remover left in them.

Plug the lines, fill with denatured alcohol and let sit for a couple of days, drain and blow out with compressed air.

When you bleed the brakes with silicone fluid, go the old fashioned route and have someone sit behind the wheel and pump the brakes S-L-O-W-L-Y. Very slow, deliberate, full strokes, no jack-rabbit pedal pumping. It's more difficult to get all of the air out of silicone fluid, you will have to bleed the brakes a couple of times to get all of the air out. Bleed them, drive the car for a bit and do a re-bleed.

After that you'll be set for a long time.

The old guy is right, you may go through a stop light switch, perhaps there is a modern switch available for your car, the new switches are better with silicone fluid.

[Terry Bond]

And the best part of all - when you have a leak, it won't eat your paint! I've seen many fine restorations ruined when the brand new brake system decides to drip a little good old Dot 3 fluid onto the fire wall or fender well. There isnt a better paint stripper around.

Terry

[Dave@Moon]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The Old Guy</div><div class="ubbcode-body">If the car has a hydraulic stop light switch, carry a spare as it has been my experience that silicone fluid will make them inoperable after awhile. Some last indefinitely, and some only make it a year. </div></div>

If this ad on eBay can be trusted, the 1958 Caddy used a mechanical switch; not a hydraulic one. That's good news. Buicks from the same era used hydraulic switches which are particularly vulnerable to the leakage/corrosion described by Joe.

[Guest De Soto Frank]

Don't shake, "glug" , or otherwise agitate the DOT-5 fluid when filling the MC. It aerates very easily. (you will have spongy brakes).

I'm one of those guys whose car "kept eating stoplight switches" after switching to DOT-5. Car in question is a '41 De Soto .

I rebuilt the entire brake system, replacing ALL hydraulic parts; no "wet" parts had been previously exposed to DOT-3 fluid.

I replaced the original hydraulic stoplight switch with a new one, to avoid any possible contamination issues.

After a few months, I noticed that the brake lights weren't coming on with normal pedal pressure; it required far more pedal effort to activate the brake lights than it did to stop the car. I replaced the switch with another new one (all were KEM brand, and new jobber stock; not ancient stuff from a "specialist").

Finally after going through 3 stoplight switches, I decided that they simply didn't like the DOT-5 fluid, and I adapted a mechanical switch from a '47-'54 Chevy truck, the kind that "rides" the brake pedal arm.

No further brakelight problems.

Aside from that, I have had no problems caused by the DOT-5 fluid after 10 years/ 30,000 miles on my De Soto.

Good luck !

[Owen_Dyneto]

There is really a very simple answer to this question. If your collector car sees regular use at normal operating temperatures, you won't see any more brake problems attributable to the brake fluid than you see in your modern everyday car. If your car sits idle for prolonged periods of time, is used for short occasional trips, and/or is stored in humid conditions, then Silicone brake fluid is the way to go. And yes, it sure does like to chew up some hydraulic stop light switches with great regularity. I'm specifically referencing the ones in the torsion-bar Packards with the extra circuit in the SL switch to kill the load-leveler when the brakes are applied. And these little devils are now priced out of sight.

[57plymouth]

I use DOT 5 and have been very happy.

[Dave@Moon]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> If your car sits idle for prolonged periods of time, is used for short occasional trips, and/or is stored in humid conditions, then Silicone brake fluid is the way to go. </div></div>

It's a <span style="text-decoration: underline">rare</span> collector car that doesn't meet at least 2 of these. That's why people reccommend DOT5 so often.

[Guest peter packard]

I am a great believer in Silicone brake fluid, as some of my cars have stood for up to seven years without use. However I recently ran into a problem with Silicone brake fluid in my 1956 Packard Patrician. I flushed the system in 2005 and converted it to silicone brake fluid ( from kanters at $US45 per gallon verses $US80 per litre in Australia.) I also reconditioned the power brake booster. Recently I started to notice a hot smell, which I took to be a manifold gasket sealer, but it turned out to be the brake linings. This came to a head when the brakes locked on and I had to release them by venting the fluid. This was compounded by the torsion level suspension not operating while there is pressure in the brake system. This occured three times and I decided that the problem appeared to bet that the approx 7% seal swell in the silicone fluid was enough to allow the main piston seal to cover the compensator port and prevent the fluid return when the brake pedal was released. I have now changed the fluid to a Dot 4 PLUS Valvoline product (8505), although I did not change the seals. I am not a real fan of Valvoline but this was one of the few synthetic brake fluid's available, and I am hoping it gives me the same results, without the seal swell. I have installed a telltale brake light under the dash to indicate when there is brake pressure in the system and so far ( 3 months) the light has gone out instantly when I release the brake pedal.

I based my conclusion on the fact that I have ruined two new master cylinders on my son's Datsun with silicone fluid. The cylinders must have very close tolerances and the seal swell locks up the system. At $A400 per unit it is an expensive exercise.

I still like silicone fluid but there is a down side as well.

[Steve Braverman]

A friend had an experience similar to Peter's with a 1930 Franklin years ago using silicone fluid. His brakes started to self-apply after driving for a few hours. At the time we attributed the problem to the greater volume of fluid in an early 30s car as compared to a more modern car. We thought that the fluid was expanding due to altitude or heat and causing the brakes to lock up. Does anyone have a more solid answer as to why this happened, and is anyone else using silicone fluid in a large early car?

[ply33]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sdbraverman</div><div class="ubbcode-body">A friend had an experience similar to Peter's with a 1930 Franklin years ago using silicone fluid. His brakes started to self-apply after driving for a few hours. At the time we attributed the problem to the greater volume of fluid in an early 30s car as compared to a more modern car. We thought that the fluid was expanding due to altitude or heat and causing the brakes to lock up. Does anyone have a more solid answer as to why this happened, and is anyone else using silicone fluid in a large early car? </div></div>

1933 is not all that early, but the last brake rebuild on my 1933 Plymouth was in 1997/98 when everything, including all tubing along the chassis, was replaced. I used silicone fluid. Other than the initial issue of getting all the air out I have had no problems. All I have had to do since then has been minor adjustments to compensate for brake shoe wear.

My car has a hydraulic brake light switch. So far I have experienced no issues with that switch and the silicone fluid.

[mrpushbutton]

Ply33--your experience is exactly what I had with the large collection. I might include that the conversion to silicone was part of a total brake system rebuild with new hard lines when necessary, new brand name (Raybestos or Wagner) wheel cylinders with steel pistons rather than the old alloy pistons, brand new rubber parts made from the latest rubber compounds. If we could not get a new (replacement) wheel cylinder I matched the diameter and width with a new cylinder then had the original cylinder sleeved then bored/honed to fit the new hardware. Done, no problems.

[Guest AntarcticDave]

Has anyone had experience with the DOT 3 & 4 compatible synthetic brake fluids? I'd read some cautions about high altitude and DOT 5 so went with DOT 3 again in my 47 (had her at 11,800 feet last weekend on a 610 mile drive). I'm thinking something like http://www.valvoline.com/pages/products/product_detail.asp?product=51 would be a good compromise to control moisture.

[Guest De Soto Frank]

Last full-system rebuild I did was about 5 years ago on a '64 Valiant.

I used DOT-4 fluid. Have not had any problems as a result, but as it has a master cylinder that vents to the open atmosphere, I would imagine that the potential exists for the fluid (still glycol-based) t oabsorb moisture from the humid Northeast air...

I drive the car perhaps once a month; not a lot.

I check the MC each time before leaving the garage, but have not had to add any fluid, nor have I had any issues from the brakes (which are "modern" Bendix self-adjusting).

I don't think I would use DOT-5 in a "modern vehicle" whose brake parts are still readily available & reasonably priced.

As to the other issue cited, with the Franklin and Packard whose brakes began "self-applying" after DOT-5 rebuilds, I have seen this happen with a variety of 1936 to 1970's vehicles; the immediate cause is usually a blocked relief port in the "floor" of the Master cylinder reservoir: sometimes due to dirt & corrosion, sometimes due to not enough clearance on the brake-pedal push rod; sometimes due to a balky power booster ('63 Dodge 880).

Most of the MC's I've worked on (non Franklin or Packard), the relief port is tiny - about 1/16" diamter or less, so it doesn't take much to plug-it up; I could envision swollen cups in an MC causing such a circumstance.

My worst experience with DOT-5 was on the '41 De Soto, using an old-time pressure bleeder (no diaphragm to separate the air and the fluid), and I inadvertantly "frothed" the DOT-5 when I aired-up the bleeder tank. I then sent that DOT-5 Frapp`e through the hydraulic system of the car. I went around the car with the hose & jar three times, was still getting bubbles, and still have very spongy brakes.

It took a call to the tech dept of the fluid mfr (Cartel; at $25 per qt (1997), they are aptly named!), and after about 15 minutes of describing/discussing the situation, their tech figured out what must have occured. He suggested letting the car stand for a few days, with the MC un-capped (covered with a clean rag to prevent debris from falling in), then CAREFULLY filling the MC, and gently pedal-bleeeding with a helper.

I followed those instructions, and got the system successfully bled, firm pedal, and has operated reliably ever since - about 30,000 miles / 10 years. The only subsequent issue was the repeated stop-light switch failure, and that was resolved by converting to a mechanical switch.

I don't know if I'll do DOT-5 on another antique...

[Guest peter packard]

I should add that I have a 38 packard which I converted to silicone in 1972, a 38 Super which I converted in 1988, also a 53 Packard in 1991, and have had no problems. I have also converted a 78 Mercedes 450SE to silicone with no adverse affects. There are some vehicles which appear to be very readily affected by seal swell, in the case of the 56 Packard Power brake system,one of the probable causes in the Shop Manual fault finding listing was swelling of the main piston seal. This could be a characteristic of the Esa-matic booster, so I would be very cautious about recommending they be converted to Silicone. I was very relieved when the brake binding ceased after a change to a non seal swell fluid. This may suggest (and I am hoping) that the seal swell from Silicone fluid may not be permanent, as the silicone leaches out from the seal.

The new generation dot 4 fluids state that they have very low water absorption and no seal swell. Good luck.

[FireballV8]

Well, thanks for all the tips and info, I finally finished installing all the new components including new stainless steel lines, hoses, cylinders, etc and filled the system with DOT 5 and bled the system. I had no trouble bleeding the system and was very careful not to get the fluid agitated. I'll try to drive the car sometime this week and hopefully it will stop.

Thanks Again.

Steve